1. Technical Field
The present disclosure relates to a turbo machine.
2. Description of the Related Art
Existing turbo machines include a thrust bearing and a radial bearing, which are independent from each other. The thrust bearing supports an axial load (thrust load) generated due to a differential pressure between both surfaces of an impeller. The radial bearing supports a radial load. Some turbo machines include an angular ball bearing for supporting the thrust load and the radial load. Tapered roller bearings are known as bearings for supporting a rotating shaft. Moreover, turbo machines including an air bearing or a water bearing are known.
FIG. 7 illustrates an air bearing device 500 described in Japanese Unexamined Patent Application Publication No. 58-196319, which includes a rotating shaft 501, a bearing member 503, a bearing member 504, an air bearing 506, an air bearing 507, a flow passage 508, and a flow passage 509. The air bearing 506 is disposed between the rotating shaft 501 and the bearing member 503. The air bearing 507 is disposed between the rotating shaft 501 and the bearing member 504. The flow passage 508 is formed in the bearing member 503, and the flow passage 509 is formed in the bearing member 504. Pressurized air is supplied to the air bearing 506 through the flow passage 508. Pressurized air is supplied to the air bearing 507 through the flow passage 509. The air bearing 506 and the air bearing 507 are tapered, and the large-diameter side of the air bearing 506 and the large-diameter side of the air bearing 507 face each other.
A pressure sensor 515 is disposed on the bearing surface of the bearing member 503. The pressure sensor 515 detects the pressure P in the air bearing 506, and an output signal p from the pressure sensor 515 is transmitted to a computing unit 516. The computing unit 516 converts the pressure P into a bearing clearance C and uses the bearing clearance C or the pressure P as a control signal. The value of the bearing clearance C is changed by moving the bearing member 503 rightward or leftward in FIG. 7 using a feed motor 514 so that the output signal p has a predetermined value. Thus, the bearing clearance C is maintained at the optimum value.
FIG. 8 illustrates a heat pump system 600 described in Japanese Unexamined Patent Application Publication No. 2007-224868, which uses water as a working fluid and which includes a water bearing. The heat pump system 600 includes a compressor 634 including a first compressing unit 633 and a second compressing unit 632. In the compressor 634, an impeller is connected to a rotor shaft. The rotor shaft of the compressor 634 is supported by a bearing 651. The bearing 651 is a water bearing. Lubricating water, which is supplied from a water supply system 653 to the bearing 651, absorbs frictional heat while functioning as a lubricant near the bearing 651. In the heat pump system 600, the temperature of lubricating water supplied to the bearing 651 is set to be equal to or lower than a temperature that is the difference between a lubricant-water set temperature (the saturation temperature −15° C.) and an increase in temperature when lubricating the bearing. Thus, reduction in the reliability of the bearing 651 is suppressed.